A highly sensitive chemical analyzer of molecular gases is presented. It is based on measurements of molecular absorption in high resolution spectra obtained with infrared tunable diode lasers (TDL). To transmit radiation from lasers to an analytical cell and back from the cell to detectors, infrared fibers with low optical losses are used. A multipass optical cell is used to enhance a sensitivity of the sensor. Various gaseous molecular objects could be detected by this analyzer due to wide spectral range of available TDLs and fibers. Use of fibers for laser radiation transfer could provide remote monitoring, multicomponent mixture analysis, and evanescent wave spectroscopy of gases in the near future.